You either receive or qualify for Social Security retirement cash benefits

OR

You currently reside in the United States and are either

A U.S. citizen or

A permanent U.S. resident who has lived in the U.S. continuously for five years prior to applying

How you enroll at age 65 depends on whether or not you are already receiving Social Security retirement benefits or Railroad Retirement benefits.

How much you have to pay for your Medicare coverage depends on your work history (if and how long you have paid Medicare taxes). Everyone has to pay a monthly premium for their medical insurance (Part B). Most people with Medicare get their hospital insurance (Part A) premium-free.